| Summary: | In this thesis, the effect of precipitation, including the melting layer, on wireless
communication systems is examined.
A melting layer model is developed which is based upon the most reliable data, available
from radar and direct observations. The dominant factor in determining the level of
reflectivity and attenuation in the melting layer is found to be the initial-snow density; its
average and bounding limits are derived in this work.
Several meteorological models (Awaka, Capsoni and ITIJ-R models) are used to develop
interference models. These models are modified to include the effect of the melting layer.
The results show that while the melting layer can on occasion affect interference, its role
overall is small and offers little improvement in interference prediction. A notable
exception is at the lower frequencies (f = 4 GHz) where melting layer enhancement of
interference is quite noticeable. It is also concluded that it is unlikely the melting layer
will be included into standard interference prediction techniques because of the high
computation cost it entitles.
While the effect of the melting layer on interference prediction is found to be minimal,
the opposite is true for the ice/snow region situated above the melting layer, especially at
high frequencies. Variations in modelling this region yielded substantial variations, in the
predicted interference levels. Interference effect is also examined on low-gain fixed and mobile terminals. This effect is
found to be debilitating for reliable communication. This makes frequency sharing
between services a risky proposition.
The Awaka meteorological model is also used as a basis to develop an attenuation model
for satellite links that include the effect of the melting layer. Several links, which are part
of the Advanced Communications Technology Satellite (ACTS) program, are used to
study the effect of the melting layer on total attenuation. It is shown that, while the
melting layer's effect is small at low latitudes, the opposite is true at high latitudes.
Simplified models for specific, total and excess attenuation in the melting layer are
developed and simple procedures to use these models in conjunction with traditional rain-only
attenuation models are presented. These were shown to agree well with predictions,
using the rigorous approach. This study is relevant for the new generation of satellite
networks geared toward the delivery of low-cost bandwidth to small businesses and
homes.
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